How many positive integers are there whose digits strictly increase from left to right?
(For example, 28, 13589, and 4 are all such integers. "Strictly" means no two digits can be equal, so 15668 wouldn't count.)
+118608
How many positive integers are there whose digits strictly increase from left to right?
(For example, 28, 13589, and 4 are all such integers. "Strictly" means no two digits can be equal, so 15668 wouldn't count.)
e.g.
How many ways can 5 digits can be chosen from 9
9C5 = 126
Each of these will have only 1 number in the order needed.
So that is 126 in 5 digit numbers
Do 1 digit numbers and/or 0 count?
there are 10 of those.
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1 digit numbers 10 (includes 0)
2 digit numbers 9C2 = 36
3 digit numbers 9C3 =84
4 digit numbers 9C4=126
5 digit number 9C5 = 126
6 digit numbers 9C6=84
7 digit numbers 9C7=36
8 digit numbers 9C8=9
9 digit numbers = 1
10+36+84+126+126+84+36+9+1 = 512 ways
